If $x= \large\frac{1}{2} \bigg(\sqrt 7+\large\frac{1}{\sqrt 7}\bigg)$ then $\large\frac{\sqrt {x^2-1}}{x- \sqrt {x^2-1}}=$

Question

\[\begin {array} {1 1} (1)\;1 & \quad (2)\;2 \\ (3)\;3 & \quad (4)\;4 \end {array}\]